1. Field of the Invention
The invention relates to a torque wrench having a head comprising an engaging member capable of being coupled antirotatingly with a screw or the like, a handle lever movable within limits relatively to the engaging member and a load sensor provided between the engaging member and the handle lever and controlling an indicating means.
2. Brief Description of the Prior Art
Torque wrenches are used to measure the tightening torque of screws. Along with the progressive technical development, these tools are gaining more importance for assembly and mounting operations with complex technological implements calling for high requirements as to accuracy of tightening torques of screws. The known torque wrenches are operated either mechanically or electrically. As for mechanical torque wrenches, the tightening torque strains a mechanical expansion or torsion body whose deformation is made visible on a scale. In the electric instruments, the mechanical expansion or tension is converted into an electric voltage via wire strain gauges as converter elements. The value of the voltage can be made visible by means of an electric indicator. The electric torque measurement involves a high current consumption compared with the known torque wrenches so that the instruments tend to be heated, on the one hand, thus affecting the accuracy of the indication, on the other hand. Furthermore, the instruments have a high weight which strongly restricts their possible use. In addition the resistance wire strain gauges tend to fatigue, thus the accuracy of indication is additionally impaired.